This invention relates to fluid brake control systems, and while the invention is subject to a wide range of applications, a preferred embodiment of the invention will be particularly described as applied to a fluid brake control system having an improved quick service and accelerated release control device.
The present invention is an improvement over currently used quick service and accelerated release control devices such as the quick service and accelerated release control devices of the well-known ABD control valve generally used for governing the brakes of freight cars. In the ABD valve, a form of quick service function is provided by the service slide valve but to provide repeated quick service cycles as long as the brake pipe pressure continues to be reduced from an extraneous source, the ABD valve must be supplemented by a special quick service control device such as the well-known B1 quick service valve.
The accelerated release function as provided in the ABD valve requires separate control devices for service and emergency release functions respectively. The ABD device for accelerated service release senses relative brake pipe and auxiliary reservoir pressures, while the accelerated release for an emergency brake application is provided by the actuation of a spool valve associated with an emergency release slide valve.
These valves as provided in the ABD valve are costly to manufacture and are somewhat slow to respond because of sliding friction. Smooth and quick application and release of brakes of a train is dependent upon the speed at which a change in control is sensed by each car and passed along from car to car, beginning at the front end of the train. It is therefore very important that there be as little delay as possible in the successive operation of the quick service and accelerated release valves on the respective cars of a train. It is therefore highly desirable to increase the speed and integrity of propagation of a brake control signal through a train over the rate of operation currently possible with ABD slide and spool valves.
An object of the present invention is to provide a fluid brake control system having improved quick service and accelerated release valves which substantially obviate one or more of the limitations and disadvantages of the described prior system.
Another object of the present invention is to reduce the number of control devices required to provide the functions of quick service and accelerated release controls.
Another object of the present invention is to reduce manufacturing and maintenance cost of brake application and release control devices.
Other objects, purposes and characteristic features of the present invention will be in part obvious from the accompanying drawings, and in part pointed out as the description of the invention progresses.